Parfit inaugurated several new areas of moral philosophy. The one that has most shaped my worldview, and which is covered in this chapter, is population ethics—the evaluation of actions that might change who is born, how many people are born, and what their quality of life will be. Secular discussion of this topic is strikingly scarce: despite thousands of years of ethical thought, the issue was only discussed briefly by the early utilitarians and their critics in the late eighteenth and nineteenth centuries, and it received sporadic attention in the years that followed.6 The watershed moment came in 1984 with the publication of Parfit’s book Reasons and Persons.
Population ethics is crucial for longtermism because it greatly affects how we should evaluate the end of civilisation.–William MacAskill (2022) What We Owe The Future, p. 168.

This is the fourth post on MacAskill’s book. (The first one is here which also lists some qualities about the book that I admire; the second one is here; the third here.) MacAskill’s note 6 refers to the Mohists, who are not treated as population ethicists because “they did not discuss the intrinsic and instrumentalist benefits and costs of increasing population.” (307) Let me grant, for the sake of argument, that such an economic analysis (costs/benefits) is intrinsic to population ethics.

It’s unclear why we should exclude non-secular population ethicists (starting with Plato, but not least Berkeley, Malthus, and Nassau Senior all of whom shaped the early utilitarians), although (recall) Parfit has soft-Nietzschean reasons for doing so, but it is left unclear whether MacAskill endorses these. Even so, MacAskill’s historical claim is odd. Some of the most important innovations in early twentieth century social and biological sciences and statistical technique (associated with names like Galton, Pearson, Fisher, Edgeworth, and Haldane)* are intertwined with population ethics (and eugenics). I am almost inclined to joke that in their age we even developed a fallacy, ‘the naturalistic’ one so as to avoid tainting doctrines with their sordid origins.

While undoubtedly some early utilitarians were pioneering population ethicists, it seems unfair to ignore the pre-utilitarian population ethicists of imperialists political arithmeticians like William Petty (seventeenth century), who put the art of managing populations by modern states on a more scientific footing while terrorizing the Irish. The managing of the size and quality of populations was an intrinsic part of the (quite ‘secular’) art of government in the reason of state tradition of the sixteenth century, too. In fact, civilizations (including feudal orders) that emphasize ‘good breeding’ (a phrase that had a positive connotation until quite recently) are generally self-consciously engaged in population ethics (even if their cost-benefit analysis deviates from MacAskill’s).

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